Radio receiver



Oct. 22 1940. I F. ANDREWS I 2,

RADIO RECEIVER Original Filed Jan. 9, 1939 uunaullll nlmllluhrl lql a MM ATTORNEYS Patented Oct. 22, 1940 llNlTED STATES PATENroFFICE 2,218,501 RADIO RECEIVER Edward F. Andrews, Chicago, Ill. Originalzapplication January 9, 1939, Serial No.

249,908. Divided and this application July 17, l 1939, Serial No. 284,865

10 Claims.

This application is a divisional from my copending application Serial No. 249,908, filed J anuary 9, 1939, which was a divisional from application Serial N0. 665,0'74, filed April 8, 1933, issueddanuary 10, 1939, as United States Patent 2,l4.-3,5 32. I

This invention relates to radio receivers and hasfor: one of 'its objects the provision of an improved radio receiver.

A further object of the invention is to provide an improved; receivercomprising a main unit and a remote control unit operatively connected by a cable, the mainunit containing power supply elements, and, both said units containing parts of the radio receiver distributed advantageouslyto maintain the remote or control unit of moderate size for convenient installation at a desired position.

A- further object of the invention is to provide an improved superheterodyne radio receiver comprising a acontrol mm, separate from the main unit. T l

A further object of theinvention is to provide a thermostatic relay in the main unit of a radio receiver'adapted to operate after a manual con- 1 trol in the: remotelylocated control unit is operated.

A further object of the invention is to provide in a radio receiver a manual control for the filament currents and a delay relay for the B supply energized by said manual control.

A further object ofthe invention is to provide a radio receiver adapted to be energized by low voltage direct current and including means comprising a filter for providing high voltage direct current, said receiver comprising a speaker having two field windings, one winding being energized by the source of low voltage direct current and the other Serving as a choke coil in said filter.

Other objects advantages, and capabilities of my invention will appear from the following description of preferred embodiments thereof, taken inl conjunction with the accompanying drawing which is a wiring diagram of a radio receiver embodying the invention.

Referring to the drawing, it is to be noted that the receiver comprises a main-unit l0 and the remote control unit 26. The physical structure of the main unit Ill and the remote control unit 26' may be that described in said Patent 2,1 i3,532.

Energy is supplied to the main unit it by a cable Hi8, this cable comprising conductors Hi9, H0 and HI enclosed within a conductive shield H2 insulatedfrom each other by suitable insued to the positive terminal of the battery 25. The conductor I H and shield I42 are connected to the negativegrounded terminal of the battery. The shield I l2 is grounded at the main unit l0, The main unit H5 is connected to the remote control unit 26 by means of afiexible. multi-conductor cable 21 of suitable length.

The remote control'unit 26 contains athermionic tube 28 and variable condensers 49, 5i and 59 ganged together for manual operation. A manual volume control is provided in the remote control unit 26. This control may comprise a rheostat or potentiometer 52 and actuated arm 53. Anincandescent lamp- 3'! is provided toilluminate the condenser scale (not shown) and to indicate that the switch 38 is on.

The receiver herein illustrated is a superheterodyne set of which the tube 23in the remote control unit 26 is the oscillator and first detector. The tubes 39, 40 and M which are located in the main unit are intermediate frequency amplifying tubes; The-tube 43 contains two diodes and atriode in the same envelope, all having a common cathode. One diode plate 94 serves as a second detector, the other diode plate serves as a source of automatic volume control potential which is applied tothe grids of tubes 39 and 40, a portion thereof being applied to the grid of tube 4!. power tube, the output of which is supplied to the voice coil of ,the loud speaker I6 through an output transformer 45. r g

The antenna conductor 46 preferably enters the cable 21*in or'near the main unit and extends through agroundedmetal shield 93 in the cable to thevremote control unit 26, being connected therein to a primary coil 41 of the antenna input system which is of lower impedance than would be required to match the antenna employed, in viewof the capacity through the cab1e.= The coil41 is inductively coupled to a coil 48, which is tuned by the condenser 49. The coil 41 is connected to a point of the coil 48 53 is coupled with the coil '56. The coil 54 is The last tube 44 is an audio frequency comparatively near the grounded end thereof -45 coupled with coils 51 and 58. Coil 58 is tuned by the condenser 59. The output of the tube 28 energizes coils 54 and 58, which in turn energizes feed-back coil 51 causing tube 28 to oscillate. The result of this oscillation, in combination with a signal is the production of current of intermediate frequency in coil 53 which in turn is communicated to coil 56 for transmission to the main unit.

The switch 38 is connected to conductors 60 and GI which extend through the cable 21. One end of the volume control resistance 62 is grounded, and the conductive arm 63 is connected to a conductor 64 which extends through cable 21. The conductor 64 is connected through a low resistance 88 to the cathode of tube 4|. This cathode is also connected through a high resistance 89 to the screen voltage line 90. The cable 21- also includes a conductor 65 which supplies filament current from the main unit to the tube 28 and lamp 3'|. Conductor 55, previously referred to, supplies B current from the main unit to the plate of the tube 28.

The remote control unit is preferably contained within a metallic housing 66 which is conductively connected to shield 93 and to ground conductor 61, which is preferably also a metallic shield, extending between the remote control unit 26 and the main unit I through the cable 27. The shield 61 contains the conductor 68 which carries the output from the coil 56 to a coil 69 in the main unit. The conductor 68 is connected to one end of the coil 56, the other end of this coil being grounded, preferably to the shield 61. The shield 61 effectively prevents any undesired signals from being picked up by the conductor 68 and introduced into the input of the intermediate frequency amplifying tubes 39, 40 and 4|.

The main unit I0 will now be described. The coil 69 is inductively coupled to the coil which is connected to the input of the tube 39. The plate circuit of the tube 39 is coupled with the input of the tube 40. The plate circuit of the tube 40 is coupled with the input of tube 4|. The plate circuit of tube 4| is coupled to the diode element 94 of tube 43, which supplies a rectified voltage to the grid of the triode elements of tube 43. The plate of these elements is coupled to the input of tube.

The triode elements of tube 43 act to amplify the output of the diode constituted by plate 94 and the cathode at audio frequency. The detected signal appears across the resistance 96 and is impressed upon the grid of the tube 43 through the filter resistor 91 and the capacity 98. The tunedintermediate frequency transformer 99 connected to the plate of the tube 40 steps down the output of that tube and feeds a signal of reduced amplitude to the grid of the tube 4| by means of the winding I00. This winding is here shown tuned to the intermediate frequency for additional selectivity. Thus there is little or no over-all gain from the last intermediate stage of amplification, including the tube 4|. Certain desired results are attained by this stepping down the output of the tube 40 into the tube 4|. In the first place, excessive difference of potential betweenthe diode plates 94 and 95, which might cause oscillation in the tube 4|, is avoided. In the second place, the grid swing of the tube 4| is kept within proper limits. In the third place, by taking practically all the gain in the first intermediate frequency tubes, substantially the maximum gain is available in the plate circuit of the tube 40, which is the source of automatic volume control energy. Any gain taken in the stage containing the tube 4| would not add anything to the automatic volume control voltage. The tube 4| is of the variable mu type so that a large variation of the potential diiference between the cathode and the grid may be employed to give the desired range of volume control.

Even when a variable mu tube is employed, it is desirable to limit the grid swing to avoid distortion. This is accomplished by impressing a stepped-down signal on the grid of tube 4|, as previously described. The signal is then amplified up again to the desired value in the tube 4| and the transformer IOI, from which it is impressed upon the diode plate 94, which acts as the second detector. The transformer 99 includes a secondary winding I02 which supplies potential to the diode plate 95 which is rectified and appears across the resistance I03. This direct current potential is utilized for automatic volume control.

The main unit l0 comprises an interrupter '14, a transformer I5, and a rectifier 16 which is associated with winding I04 and condensers 18 for the purpose of ironing out fluctuations in the direct current and potential delivered by conductor 79. This conductor is connected in known manner to the plate circuits of tubes 28, 39, 40, 4|, 43, and 44. The filament current for all the tubes is derived from the battery 25 through conductor I09 which passes to the main unit I0, and is connected therein to the conductor 60. When the switch 38 is thrown to made position, the conductor I09 is connected to conductor 6| of the cable 21 and to conductors 8| and 82 in the main unit I0. The current for the filament of tube 28 flows back to the control unit through conductor 65 of the cable 21. The conductor 82 is connected to the heating coil I01 of the normally open thermostatic switch I06.

The field of the loud speaker comprises the winding I04 and another winding I05. The winding I04 is connected in series with the plate voltage supply from the secondary of the power transformer through the rectifier tube I6. The winding I04 acts as a choke coil to filter the plate supply, as well as supplying part of the energy to the speaker field. Only a part of the speaker field energy is supplied from the plate supply, the remainder for bringing the speaker to the proper sensitivity being supplied directly by conductor I I0 and switch I06 from the battery to the coil I05. By properly proportioning these coils, the speaker field can be employed as a choke coil and the proper speaker sensitivity attained with a vibrator of moderate output.

To avoid operating the vibrator without a load, it is desirable that the filaments of the tubes should have attained their operating temperature before the vibrator is connected to the battery. The thermostatic relay I06 fulfills this purpose. This relay is adapted to be operated by the heating winding I01 which is energized upon the closing of the switch 38. The Winding I01 is in parallel with the filaments of the tubes and the current therefor is derived from the battery. The thermostatic relay is proportioned to close the vibrator circuit after the cathodes have attained operating temperature. The thermostatic switch is preferably temperature compensated so that its time interval is not extemperature.

The thermostatic relay serves both as a delayed switch and as a remotely controlled relay. The vibrator current does not pass through cable 21, thus reducing the liability of the introduction of undesirable electrical disturbances into the amplifier tubes, and also avoiding the larger conductors or higher voltage drop which'would be occasioned by a higher current through the cable.

The vibrator or interrupter 14 comprises a casing 84 including sound insulating material, in which is enclosed an electro-magnet 85 which controls points 86 in series, with the windings of said magnet so as to cause continual interruption in the current flowing through the primary of the transformer 15. Acondenser 81 and high re sistance 88 are provided both across the winding 85 and points 8E.-

The continual interruption of the flow of current through the contacts 86 develops undesired high frequency disturbances. It is important, particularly where an interrupterpower supply is made a part of the radio receiver, to isolate these high frequency disturbances and to prevent them from being amplified by the tubes of the receiver so that they appear as objectionable noises in the speaker output. To isolate these disturbances, the outer contact 85 and the metal shield 84 around the interrupter are grounded at the main unit and through conductor HI to the battery 25. The grounding of one side of the circuit in this manner tends to reduce to a minimum the potential differences between the various parts connected thereto. Thus, there is relatively little tendency for the undesired high frequency disturbances to reach the tubes through the grounded side of thecircuit. The interrupter coil 85 and the primary of the transformer 15 are interposed between the ungrounded contact 86, at the sourceof the undesired dis turbances, and the various'conductors connected to the ungrounded side of the circuit from which the undesired high frequency disturbances might be radiated to the tubes, or through which the disturbances might be carried to the tubes by conduction. The inductance of these coils presents a high impedance to the passage of these high frequency .disturbances. The condenser 81 which bridges from the connected ends of the coil 85 and the primary of the transformer 15 to ground, forms a low impedance path to ground tending to short-circuit that portion of the undesired high frequency disturbances which may pass through the coil 85. Thus, by connecting one of the contacts 86 directly to the common ground, the coil 85, the condenser 81, and the primary of the transformer 85 form a filter effective for isolating the undesired disturbances from theungrounded side of the circuit through which they wouldotherwise be transmitted to the tubes. It is preferred to locate one or more of the inductances constituting the filter for undesired components adjacent the interrupter points and to shield the interrupter contacts and adjacent portions of the interrupter circuit, including all or part of the inductances and the condenser forming the high frequency filter with grounded shielding means. tube filaments are connected to the line 8|, the filament of tube 28 being connected thereto by line 65 of cable 21, and the filament of tube 16 being connected thereto by line 82. Choke coils 9! are provided in the filament current circuit,

being preferably arranged in series: in the filament supply circuit, serving with the filament The ungrounded sides of the resistance to provide an induction-resistance filterwhich effectively filters out high frequency disturbances produced by the vibrato-r 14 and which may not be completely isolated by the means above described. This filter, including thechoke coils 9!, is also effective in preventing undesired high frequency disturbances originating'ln the ignition or battery charging system of the automobile from reaching the tubes. It will be seen that the filtering effect is greatest towards the input end of the receiving set, where any disturbance present would be amplified to the greatest extent. i

The "choke coil 92 is connected in series with the lead 55 which supplies plate current to the tube 28. This choke coil prevents oscillation which might be caused by disturbances passing through lead 55, coil 53 and the plate ground capacity of the tube 28.

It is preferred that the rectifying tube '56 passes current when the points 86 make contact, rather than when the break contact. The change from one condition to the other may be effected in many ways, one way being to reverse the connections of the secondary winding of the transformer I5. The set can thus be readily adapted for any automobile, regardless of which pole of the battery is grounded.

The battery cable I08 comprises the three leads ,IUS, Ill! and Ill, surrounded by a shield 1 f2, one end of which connects to the chassis of the main .unit, and the other to the grounded terminal of the battery. The conductor I09 is connected to the ungrounded terminal of the battery and leads to the switch 38 for the filament and heating element I01 supply. Conductor I I0 is connected to the positive terminal of the battery and leads to one contact of the thermostatic relay I06, through which it is connected in parallel through the primary winding of thetransformer I5 and vibrator H on the one hand, and through coil I05 on the other hand, to conductor l H which is connected to the negative terminal of the battery. In the drawing I have shown the negative terminal of the battery to be grounded.

Should the receiver be employed in an automobile in which the positive terminal is grounded, then shield I I2 and conductor I 10 should be connected to the positive terminal of the battery, and conductors I69 and Ill should be connected to the negative terminal of the battery. It is to be noted that this hook-up follows the nomenclature of the preceding paragraph, according to which shield H2 is grounded and conductor I09 is connected to the ungrounded terminal, and lead Hf! is connected to the positive terminal while lead III is connected to the negative terminal.

The operation is as follows: The switch 38 beingclosed, the circuits through the filaments and resistance l0! are made. By the time the filaments have attained their operating temperature, the thermostatic switch I96 has closed.complet- 'ing the circuit through the vibrator I4 and the power. connection of the grid 4| to the resistor H, it is tive grid bias of tube 4| by making the cathode more or less positive. It is to be noted that this control in the main unit is effected from the control unit by variation of a direct current which is of practically constant value for any particular manual setting of the volume level control 63.

The automatic volume control voltage is applied to the grids of the tubes 39 and 40, which elements are ahead of the source of energy from which the automatic volume control voltage is derived, which source is the plate circuit of the tube 40. Automatic volume control voltage is also applied to the grid of the tube 4|, which is after the source of the energy which supplies the automatic volume control voltage which, as has been noted, is the plate of the tube 40. It may here be pointed out that the effective automatic volume control voltage applied to the tubes before the source of the automatic volume control energy is to decrease the gain of these tubes, and hence the automatic volume control voltage produced, so that these tubes provide only a diminishing corrective effect. However, the application of automatic volume control voltage to the rid of a tube after the source of automatic volume control energy, such as tube 40, produces a reduction of gain without any reduction of the automatic volume control voltage. By tapping in the grid connection of the tube M at a suitable point on the resistor I03, signals of substantially uniform strength can be obtained from divers stations with antenna signals of widely different Indeed, by suitable adjustment of the possible to make a stronger antenna signal appear as a weaker audible signal than that derived from a weaker antenna signal.

For the satisfactory transfer of signal energy from the control unit to the main unit, it is desired to employ the means for minimizing loss or attenuation through the cable described in my Patent No. 2,143,532, issued January 10, 1939.

While the invention is well adapted for use in automobile radio receivers, I do not intend to limit my invention to such receivers since it may be applied to home sets and indeed to any manner of set employing a remote control.

Furthermore, it is not intended to be limited to any particular type of tube since other tubes may be employed if desired, provided the bias of the control grid can be sufficiently varied without undue distortion.

Although the invention has been described in connection with the specific details of a preferred embodiment thereof, it must be understood that such details are not intended to be limitative of the invention, except in so far as set forth in the following claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is:

l. A radio receiver comprising a control unit and a main unit, physically separated but connected together by a cable, tuning means, means including a thermionic tube for converting radio frequency currents into intermediate frequency currents, means for adapting said intermediate frequency currents for transmission through said cable, and a manual volume control, all located in said control unit, intermediate amplifying, detecting, and audio-amplifying tubes in said main unit, volume level control means in said main unit connected with said manual volume control in said control unit through said cable, a loud speaker mounted in said main unit having a pair of field windings, power supply devices made as an integral part of said main unit supplying plate voltage to the plates of the tubes in both said units, said power supply devices including a transformer having a primary and secondary and a rectifier and filter system connected between said secondary and the plates of said tubes, said filter system including one of said field windings, an interrupter for continuously opening and closing said primary circuit in series with said primary and a low voltage battery, and means supplying direct current from said battery to the other field winding.

2. A radio receiver comprising a control unit and a main unit, physically separated but connected together by a cable, tuning means, means including a thermionic tube for converting radio frequency currents into intermediate frequency currents, means for adapting said intermediate frequency currents for transmission through said cable, and a manual volume control, all located in said control unit, intermediate amplifying, detecting, and audio-amplifying tubes in said main unit, volume level control means in said main unit connected with said manual volume control in said' control unit through said cable, a loud speaker mounted in said main unit having a pair of field windings, power supply devices made as an integral part of said main unit supplying plate voltage to the plates of the tubes in both said units, said power supply devices including a transformer having a primary and secondary and a rectifier and filter system connected between said secondary and the plates of said tubes, said filter system including one of said field windings, an interrupter for continuously opening and closing said primary circuit in series with said primary and a low voltage battery, means supplying direct current from said battery tothe other field winding, a delayed switch having thermoresponsive actuating means in the main unit in series with the interrupter, and a manual switch in the control unit, a conductor passing through said cable from said manual switch to the heaters of the tube and to the thermo-responsive actuating means.

3. A radio receiver comprising a control unit and a main unit, physically separated but connected together by a cable, tuning means, means including a thermionic tube for converting radio frequency currents into intermediate frequency currents, means for adapting said intermediate frequency currents for transmission through said cable, and a manual volume control, all located in said control unit, intermediate amplifying, detecting and audio-amplifying tubes in said main unit, volume level control means in said main unit connected with said manual volume control in said control unit through said cable, a loud speaker mounted in said main unit, power supply devices made as an integral part of said main unit supplying plate voltage to the plates of the tubes in both units; said power supply devices including a transformer having a primary and secondary, and a rectifier and filter system connected between said secondary and the plates of said tubes, and an interrupter for continuously opening and closing said primary circuit in series witli said primary and a low voltage battery.

4. A radio receiver comprising a control unit and a main unit, physically separated but connected together by a cable, an oscillator circuit including manual tuning means in the control unit, a manual volume control in the control unit,

intermediate amplifying, detecting, and audioamplifying tubes in the mainunit, volume level control means in said main unit oper'atively connected to said manual volume control in said control unit, power supply devices in said main unit for supplying power to the plates of the tubes, said power supply devices including a transformer having a primary and secondary and a rectifier and filter system connected between said secondary and the plates of said tubes, and an interrupter for continuously opening and closing said primary circuit in series with said primary and a low voltage battery.

5, A radio receiver comprising a main unit, a control unit and a cable providing electrical connections therebetween, radio tubes in the main unit, an interrupter in the main unit adapted to interrupt direct currentfor the provision of high voltage direct current, a delayed switch having thermo-responsive actuating means in the main unit in series with the vibrator, and a manual switch in the control unit, a conductor passing through said cable from said manual switch to the heaters of the tubes and to said thermo-responsive actuating "means.

6. In combination, a radio receiver having a thermionic tube, means supplying heater current to said tube, a loud speaker connected to the output thereof, and a source of low voltage direct current therefor, said receiver comprising an interrupter to convert partof said direct current into pulsating current, means for transforming and rectifying said pulsating current, means for supplying direct current from the transforming and rectifying means to the plate of said thermionic tube, said loud speaker having two field windings, conductors connecting one field winding to said source of low voltage direct current, and conductors connecting the other field winding to said transforming and rectifying means.

7. In a radio receiver, in combination, a main unit including a loud speaker having a field winding and a remotely located control unit, a circuit extending between said units and including a, switch in the control unit and a heater winding in the main unit, a thermostatic element in' the main unit in heat exchange relation to said winding, and circuit controlling means in said main unit in series with said field winding, controlled by said element.

8. In a radio receiver, in combination, a main unit and a remotely located unit, a manually operated switch in the remote unit, electrical means in the main unit adapted to be energized by said switch, a thermostatic relay in the main unit adapted to be controlled by said switch, and B voltage supply means and a loud speaker in the main unit adapted to be controlled by the thermostatic relay and energized subsequent to the energization of the first said electrical means.

9. In a radio receiver, in combination, a main unit and a remotely located control unit, manually operable signal control means in said control unit, signal amplifying means in said main unit, a multi-conduotor cable extending between said units and including conductors through which said signal control means controls the output of said signal amplifying means, a manually operable switch in the control unit controlling a heater winding in the main unit, a thermostatic element in the main unit in heat exchange relation to said winding, circuit closing contacts in said main unit controlled by said thermostatic element to close substantially after the operation of said switch by said element, a vibrator and associated elements in the main unit for supplying high voltage energy, said vibrator being controlled by said contacts.

10. A radioreceiver comprising a control unit and a main unit, physically separatedbut connectedtogether by a cable, an oscillator circuit including manual tuning means in the control unit, a manual volume control in the control unit including a variable resistance, intermediate amplifying, detecting, and audio-amplifying tubes in the main unit, a speaker energized from said tubes, volume level control means in said main unit including an element of one of said tubes.

connected to said resistance of said manual volume control in said control unit, whereby the output of said tube to the speaker is controlled,

power supply devices in said main unit for supplying poWer-to the plates of the tubes, said power supply devices including a transformer having a primary and secondary and a'rectifier and filter system connected between said secondary and the plates of said tubes, an interrupter for continuously opening and closing said primary cir cuit in series with said primary and a low voltage battery, and switch means in said control unit controlling the supply of energy to said power supply devices and to the filaments of said tubes.

EDWARD F. ANDREWS. 

